Agent for steel-making formed by aluminum-making slag

ABSTRACT

The present invention discloses an agent for steel-making formed by aluminum-making slag, which is used by adding to molten steel, wherein said agent comprises: metal aluminum, aluminum oxide, silicon dioxide, magnesium oxide, and calcium oxide. Said agent for steel-making is a deoxidizing agent, modifying agent, and slag regulating agent for steel-making. Said deoxidizing agent or modifying agent for steel-making may comprise by mass percentage 25-70% Al, 3-30% Al 2 O 3 , 10-30% CaO, 5-15% MgO, 3˜10% SiO 2 , and a small amount of impurities. Said slag regulating agent for steel-making may comprise by mass percentage 5-20% Al, 25-70% Al 2 O 3 , 10-50% CaO, 5-15% MgO, 3˜10% SiO 2 , and a small amount of impurities. The agent for steel-making of the present invention facilitates removing sulfur and other impurities from molten steel. In addition, the greatest advantage of this product lies in that it is capable of decreasing total cost of steel-making and improving efficiency of steel-making.

FIELD OF THE INVENTION

The present invention relates to an agent for steel-making formed by aluminum-making slag, and particularly to a deoxidizing agent, modifying agent, and slag regulating agent for steel-making.

BACKGROUND OF THE INVENTION

During the processes of deoxidizing, modifying, and slag regulating, apart from the choice of equipment, what is most important is to select a suitable deoxidizing agent, modifying agent, and slag regulating agent.

According to tests, in the deoxidizing material for modern steel-making, various elements exhibit different capabilities of deoxidizing at 1600° C. From the tests, it can be found that the capabilities of deoxidizing for various elements at 1600° C. are ranked in an order of Al, Ti, B, Si, C, V, Cr, and Mn. However, conventionally the elements like Al, Si, Mn, Ca or the like are selected for deoxidizing, while other elements are used to adjust the composition.

Currently in the steel-making enterprises, materials like aluminum bulk, Si—Al—Ba, Si—Ca alloy, Si—Al alloy, core-spun aluminum wire are primarily used for deoxidizing and modifying. Although all of these materials are excellent deoxidizing agent and modifying agent, they have a high price, and the slag after deoxidizing is thin, which is not beneficial for slag conglomeration. In addition, a large amount of woods are needed as reducing agents for producing various alloys, and the consumption of woods is very large, which is detrimental for the environment.

In the slag regulating process of molten steel, CaC₂ is used for slag regulating. However, when CaC₂ is smashed, it produces C₂H₂ gas in case of high air humidity, and such a gas is inflammable, explosive, and unsafe. Besides, the production of CaC₂ is accompanied with high energy consumption, which is not conducive to environmental protection.

SUMMARY OF THE INVENTION

In view of the drawbacks in the prior art, the present invention provides an agent for steel-making formed by aluminum-making slag, which can be used as a deoxidizing agent, modifying agent, and slag regulating agent, and exhibit excellent properties.

It is an object of the present invention to provide a deoxidizing agent, modifying agent, and slag regulating agent which is low in cost and high in efficiency.

To this end, the present invention provides an agent for steel-making formed by aluminum-making slag, which is used by adding to molten steel, wherein said agent comprises: metal Al, aluminum oxide, magnesium oxide, and calcium oxide.

Furthermore, said agent for steel-making is a deoxidizing agent, modifying agent, or slag regulating agent for steel-making.

Furthermore, said deoxidizing agent or modifying agent for steel-making comprises by mass percentage 25-70% Al, 3-30% Al₂O₃, 10-30% CaO, 5-15% MgO, 3˜10% SiO₂, and a small amount of impurities.

Furthermore, said deoxidizing agent or modifying agent for steel-making consists of the following compositions by mass percentage: 25-70% Al, 3-30% Al₂O₃, 10-30% CaO, 5-15% MgO, <3% rare earth elements, 3˜10% SiO₂, and a small amount of impurities. Namely, it only comprises the above compositions, and does not comprise other compositions.

Furthermore, each composition in said deoxidizing agent or modifying agent for steel-making is powdered shaped, with a granularity of 50 μm˜1 mm.

Furthermore, said deoxidizing agent or modifying agent powder for steel-making is pressed into a sphere shape.

Furthermore, said deoxidizing agent or modifying agent powder for steel-making, which has been pressed into a sphere shape, has a diameter of 20˜50 mm.

Furthermore, said deoxidizing agent or modifying agent for steel-making is added to the molten steel during molten steel tapping in primary melting of a converter or electric furnace.

Furthermore, said deoxidizing agent or modifying agent for steel-making is added to a ladle refining furnace or electric furnace.

Furthermore, said slag regulating agent for steel-making comprises by mass percentage 5-20% Al, 25-70% Al₂O₃, 10-50% CaO, 5-15% MgO, 3˜10% SiO₂, and a small amount of impurities.

Furthermore, said slag regulating agent for steel-making consists of the following compositions by mass percentage: 5-20% Al, 25-70% Al₂O₃, 10-50% CaO, 5-15% MgO, <3% rare earth elements, 3˜10% SiO₂, and a small amount of impurities. Namely, it only comprises the above compositions, and does not comprise other compositions.

Furthermore, each composition in said slag regulating agent for steel-making is powdered shaped or is sphere shaped by pressing powders.

Furthermore, said slag regulating agent for steel-making is added to a ladle refining furnace for slag regulating, or is added to molten steel for slag regulating during molten steel tapping in primary melting of a converter or electric furnace.

Furthermore, said deoxidizing agent or modifying agent powder for steel-making is blown into a ladle refining furnace or electric furnace.

Furthermore, during steel tapping in a converter, said deoxidizing agent or modifying agent for steel-making is added after Fe alloys are added.

Furthermore, during steel tapping in a converter, when ⅓ of the steel has been tapped, ⅔ of the deoxidizing agent or modifying agent for steel-making is added, and then when the steel tapping is complete, the remaining ⅓ deoxidizing agent or modifying agent for steel-making is added to the surface of the ladle refining furnace.

Furthermore, the dosage of said slag regulating agent for steel-making is selected so that MgO in the furnace slag reaches a saturation value.

The agent for steel-making of the present invention contains a certain amount of metal aluminum and highly active aluminum oxide. The agent for steel-making firstly reacts with oxygen in molten steel to form a highly reducing atmosphere. Then the aluminum oxide which the agent for steel-making contains and the aluminum oxide formed by metal aluminum combine together with calcium oxide to form a calcium aluminate slag system. The slag system has a melting point of about 1300° C. and a high sulfur capacity, thus facilitating removing sulfur and other impurities from molten steel. The slag system also has an outstanding effect in making white slag. In addition, the greatest advantage of this product lies in that it is capable of decreasing cost of steel-making and improving efficiency of steel-making.

According to the present invention, it is not necessary to alter the existing process and equipment, and thus it is beneficial for saving energy and reducing emission, decreasing production cost, improving production efficiency, and producing clean steel for the steel enterprise.

DETAILED DESCRIPTION OF EMBODIMENTS

The main technical solution of the present invention lies in a composite aluminum powder made from scum which is formed during aluminum smelting, and the chemical compositions of the scum are listed in Table 2.

TABLE 2 Chemical compositions of composite aluminum powder (wt %) Type Al Al₂O₃ SiO₂ MgO C granularity STQ-1 18-20 55-65 <10 2-6 <1.5 <1 mm STQ-2 30-35 45-55 <10 <5 <1.0 <1 mm STQ-3 40-45 35-45 <8 <5 <1.0 <1 mm STQ-4 50-55 25-35 <6 <5 <1.0 <1 mm STQ-5 60-65 15-25 <4 <4 <1.0 <1 mm STQ-6 70-75  5-15 <4 <4 <1.0 <1 mm

STQ-1˜STQ-6 are serial numbers for various types of scum formed during different processes of aluminum smelting to show distinction.

The above composite aluminum powder replaces metal aluminum as a reducing agent. Besides, based on the above composite aluminum powder, CaO is added to form Al—Ca deoxidizing agent, modifying agent, and slag regulating agent, and is added in different manners to perform deoxidizing, modifying, and slag regulating treatment on molten steel.

In the present invention, the deoxidizing agent, modifying agent, and slag regulating agent based on the composite aluminum powder uses different composition stoichiometry according to requirements of different types of steel. For each composition stoichiometry, the deoxidizing agent, modifying agent, and slag regulating agent can be added to molten steel in two manners, i.e., can be fed in sphere shape and powdered shape. If possible, a gas may be blown into the primary melting converter or electric furnace, or blown into the ladle refining furnace.

The compositions for agent for steel-making formed by the composite aluminum powder and CaO are listed in Table 3.

TABLE 3 Compositions of agent for steel-making (wt %) Name Al Al₂O₃ CaO SiO₂ MgO Impurities STQ-6000 70 3 10 3 5 balance STQ-5000 50 5 15-20 4 2 balance STQ-4000 40 5 20-25 6 2 balance STQ-3500 35 7 20-25 7 2 balance STQ-3000 30 10 30 8 10 balance STQ-2500 25 20 20 10 15 balance STQ-2000 25 30 30 10 3-5 balance STQ-1900 5 70 20 — 5 balance STQ-1800 20 25 50 — 5 balance STQ-1700 20 30 10 10 15 balance STQ-1600 15 35 30 5 10 balance

STQ-1600˜STQ-6000 are serial numbers of agent for steel-making with different compositions to show distinction. Furthermore, SiO₂ can be selectively removed from the composite aluminum powder. In addition, the above compositions may further comprise rare earth elements. Generally, the percentage by weight of rare earth elements is less than 3%. In addition, STQ-1600˜STQ-1900 generally are used for slag regulating, while STQ-2000˜STQ-6000 generally are used for deoxidizing and modifying.

The agent for steel-making generally is powdered shaped. The powder can be used directly, and can be formed into bulks with dimensions of 40 mm×40 mm×25 mm or 50 mm×40 mm×20 mm. The dimensions can also be adjusted according to the user's needs.

The operation method of using the above agent for steel-making as a deoxidizing agent and modifying agent is described as follows.

According to performance requirements of different types of steel, the above deoxidizing agent and modifying agent is added into a converter and electric furnace through a rear charging inlet during steel tapping in primary melting of the converter or electric furnace, or is directly added into a ladle refining furnace (LF furnace). Generally, during steel tapping of the converter or electric furnace, the deoxidizing agent for steel-making of the present invention can be added once the addition of Fe alloys is complete. The deoxidizing agent for steel-making of the present invention can replace other materials for deoxidizing completely or to a large extent. It is required to calculate the adding amount according to the steel-making process, and the calculating method is the same as the original process.

The deoxidizing agent for steel-making of the present invention is applied to the LF furnace in the following manner. When ⅓ of the steel has been tapped, ⅔ of the deoxidizing agent is added, and then when the steel tapping is complete, the remaining ⅓ deoxidizing agent is added to the surface of the ladle refining furnace. The adding amount is the same as that of the deoxidizing material in the original process.

The deoxidizing method by using the powdered deoxidizing agent and modifying agent is described as follows.

The chemical compositions of the powdered deoxidizing agent and modifying agent are the same as those of the above sphere shaped deoxidizing agent and modifying agent. The difference lies in that it is powdered shaped. The granularity is less than 1 mm. The powdered deoxidizing agent and modifying agent can be divided into small packages of 5 Kg, 10 Kg, 15 Kg or the like. As for the enterprise with a furnace volume less than 20 Tons (T) or a steel ladle less than 50 Tons, the powdered shaped deoxidizing agent and modifying agent provides better effects. If possible, a blowing method can be used, in which the adding method and adding amount are the same as those described above.

The compositions of three types of sphere shaped slag regulating agent are listed in Table 4.

TABLE 4 Compositions of sphere shaped slag regulating agent (wt %) Name Al Al₂O₃ CaO SiO₂ MgO STQ-1500 15 35 30 10 5 STQ-1000 10 40 35 10 5 STQ-500 5 47 40 3 5

The dimensions of the bulk are 40 mm×40 mm×25 mm or 50 mm×40 mm×20 mm, and the dimensions can also be adjusted according to user's needs.

The method of regulating slag for molten steel by using the sphere shaped slag regulating agent is described as follows.

During steel tapping in primary melting of the converter or electric furnace, on basis of the temperature of steel tapping and the conditions of furnace slag, the adding amount of slag regulating agent is determined to perform slag regulating. As a result, MgO in furnace slag reaches a saturation value, the melting point of furnace slag is increased, and the viscosity of furnace slag is adjusted, so that it is suitable for splashing slag. In general, the adding amount is 3-5 Kg/T.

As compared with the conventional slag regulating agent, the slag regulating agent of the present invention has better performance in slag conglomeration, and facilitates viscosifying the furnace slag. Since the slag regulating agent contains a relatively large amount of Al₂O₃, it provides outstanding protection and repair function for the refractory material.

The comparisons between the product of the invention and the existing products regarding price and energy consumption are listed in Table 5.

TABLE 5 Comparisons between the product of the invention and the existing products regarding price and energy consumption Slag Deoxidizing Existing Modifying Existing regulating Existing slag Items for agent of the deoxidizing agent of the modifying agent of the regulating comparing invention agent invention agent invention agent Price (Yuan/T) 3000-8800  8000-16000 3000-8000  8000-15000 1800-2800 2000-3500 Energy 150-200 10000-20000 150-200 10000-20000 150-200  8000-10000 consumption (KW · h/T) Using effects Same as the existing products Effects on Small Very large Small Very large Small Very large environment Reducing feeding from large labour feeding large labour feeding large labour workers' silo, greatly intensity for from silo, intensity for from silo, intensity for operating reducing manual greatly manual greatly manual conditions labour operation reducing operation reducing operation intensity labour labour intensity intensity

As for the method by using powdered shaped deoxidizing agent, modifying agent, and slag regulating agent for deoxidizing, modifying, and slag regulating process treatment, the method as described for the sphere shaped product applies.

In summary, the composite deoxidizing, modifying, and slag regulating agent of the present invention has significant effects on deoxidizing, modifying, and slag regulating during steel-making. Tests demonstrate that when the original oxygen in molten steel is 57.2 ppm, by using 2 Kg of the deoxidizing agent of the invention for deoxidizing, the final oxygen can be decreased to 10.3 ppm. Namely, the deoxidizing rate is not less than 70%. The deoxidizing agent can also serve for desulfurization (the test report is attached, see Table 7). The deoxidizing agent can also remove other impurities to improve the performance of steel. The modifying agent has a prominent effect on top slag modifying, thus decreasing the oxidability of top slag, increasing the mobility of top slag, greatly improving the castability of molten steel, decreasing consumption of deoxidizing alloys, and decreasing consumption during each stage of continuous casting. The modifying agent is free from CaF, so that it poses little erosion on the RH leaching and dipping pipes, and improves the utilization rate of equipment (the test report is attached, see Table 9).

As compared with the prior art, the present invention has the advantages of low cost, no necessity for altering the existing equipment and process, low energy consumption, significant effects, simple operation, free from fluorides and beneficial for environment protection, and belonging to green products.

SPECIFIC EXAMPLES Example 1

A deoxidizing test is performed on molten steel in 5 furnace runs by using the deoxidizing agent of the present invention.

The compositions of the deoxidizing agent are listed in Table 6.

TABLE 6 Compositions of deoxidizing agent (wt %) Composition Al SiO₂ MgO CaO Al₂O₃ P, S Content 40 <5 12 15 30 ≦0.3

Dimensions: 40 mm×40 mm×25 mm

The test conditions and process parameters of molten steel deoxidizing treatment in this example are listed in Table 7.

TABLE 7 Test conditions and process parameters of molten steel deoxidizing treatment Furnace run Items 1(210) 2(211) 3(212) 4(213) 5(214) LF ladle capacity W₁(L) 90 90 90 90 90 Actual amount of molten 91.6 91.8 92 91.8 89.7 steel W₂(t) Temperature of molten 1953 1597 1599 1600 1600 steel(° C.) Refining time(min) 13 14 13 14 15 Adding amount W_(n) 300/ W₂ 300/ W₂ 300/ W₂ 300/ W₂ 300/ W₂ (Kg/Ton) Temperature ramping rate 30/13 50/14 45/13 37/14 63/15 (° C./min) Oxygen(O) content 65.8 57.3 49.3 57.2 47.6 before refining (ppm) Oxygen(O) content after 18.3 15.2 13.2 10.3 12.2 refining (ppm) Deoxidizing rate (%) 72.19 73.47 73.23 82.00 74.3 Sulfur(S) content before 44 48 34 41 35 refining (ppm) Sulfur(S) content after 24 24 18 20 15 refining (ppm) Rate of desulfurization(%) 45 50 47 51 57 Inclusions before 26 25 30 26 71 refining (%) Inclusions after 15 12 9 20 13 refining (%)

Example 2

A modifying test is performed on molten steel in 4 furnace runs by using the modifying agent of the present invention.

The compositions of the modifying agent are listed in Table 8.

TABLE 8 Compositions of modifying agent (wt %) Compositions (%) Metal Al CaO Al₂O₃ SiO₂ RE MgO CaO Content 37.0 14.1 19.8 2.9 1.5 14.2 10.5

Dimensions: 40 mm×40 mm×25 mm

The composition analyzing table of molten steel modifying treatment in this example is listed in Table 9

TABLE 9 Composition analyzing table of molten steel modifying treatment CaO/ Furnace number FeO CaO Al₂O₃ SiO₂ MgO MnO Al₂O₃ 1913824⁻¹ 17.78 42.68 4.50 7.68 8.22 2.47 9.48 1913824⁻² 2.60 44.69 28.14 8.21 8.55 1.55 1.58 1913825⁻¹ 16.80 41.43 3.72 6.70 7.72 3.33 11.14 1913825⁻² 3.09 42.30 27.56 7.78 8.77 2.02 1.53 Average before 17.29 42.06 4.11 7.19 7.97 2.90 10.31 modifying Average after 2.85 43.50 27.85 8.00 8.66 1.79 1.56 modifying Note: ⁻¹before adding a modifying agent; ⁻²after adding a modifying agent.

After passing the RH furnace, the effects become more prominent, and the molten steel always keeps good mobility. Since the modifying agent is of a relatively high content and is free from CaF, the erosion on the RH leaching and dipping pipes is relatively low. Meanwhile, a better mobility of top slag also alleviates the problem of slag sticking to the leaching and dipping pipes. The better mobility and composition of the top slag also ensure that the top slag can well adsorb inclusions formed during deoxidizing, so that the purity and castability of molten steel are greatly increased.

Comparisons between the inlet and exit slag samples for a RH furnace are listed in the following Table 10.

TABLE 10 Comparisons between the inlet and exit slag samples for a RH furnace CaO/ Furnace number FeO CaO Al₂O₃ SiO₂ MgO MnO Al₂O₃ 1913824⁻¹ 2.32 43.41 28.87 7.96 8.09 2.67 1.50 1913824⁻² 2.17 42.91 36.61 7.74 7.58 1.37 1.17 1913825⁻¹ 2.98 43.77 27.02 8.05 8.62 3.45 1.62 1913825⁻² 2.54 41.36 34.49 7.92 9.13 1.89 1.20 Average for 2.65 43.59 27.95 8.01 8.36 3.06 1.56 inletting RH Average for 2.36 42.14 35.55 7.83 8.36 1.63 1.19 exiting RH Note: ⁻¹inletting RH; ⁻²exiting RH.

Example 3

A slag regulating treatment is performed on molten steel by using the slag regulating agent. The compositions of slag regulating agent are listed in Table 11.

TABLE 11 Compositions of slag regulating agent (wt %) Composition Al CaO Al₂O₃ SiO MgO Content 10-15 40-45 35-45 10 5

Dimensions: 40 mm×40 mm×25 mm.

In this example, the process parameters of slag regulating agent used in the steel plant are listed in Table 12.

TABLE 12 Process parameters of slag regulating agent used in the steel plant Steel LF furnace Refining time Adding amount of slag Argon blowing plant (capacity in T) (min) regulating agent (Kg) Steel type and stirring 1 100 58 5 semikilled steel Yes 2 80 36 3.5 killed steel No 3 120 60 3.2 rimmed steel Yes

The effects of using slag regulating agent in the steel plant in this example are listed in Table 13.

TABLE 13 Effects of using slag regulating agent in the steel plant Sub- Speed of Rate of Alkalinity Steel merged making desulfur- of steel plant arc effect white slag Initial S Final S ization slag R 1 good fast 0.073 0.019 73% ≧3.0 2 good fast 0.050 0.009 82% ≧2.6 3 relatively fast 0.035 0.005 86% ≧2.9 good

Although the implementations of the present invention have been disclosed above, the present invention is not limited to the applications as set forth in the description and implementations. Therefore, without departing from the claims and the general concepts defined by their equivalents, the present invention is not limited to the specific details and the legends as shown or described herein. 

1. An agent for steel-making formed by aluminum-making slag, which is used by adding to molten steel, wherein said agent comprises: metal aluminum, aluminum oxide, silicon dioxide, magnesium oxide, and calcium oxide.
 2. The agent for steel-making according to claim 1, wherein said agent for steel-making is a deoxidizing agent for steel-making.
 3. The agent for steel-making according to claim 1, wherein said agent for steel-making is a modifying agent for steel-making.
 4. The agent for steel-making according to claim 1, wherein said agent for steel-making is slag regulating agent for steel-making.
 5. The agent for steel-making according to claim 2 or 3, wherein said deoxidizing agent or modifying agent for steel-making comprises by mass percentage 25-70% Al, 3-30% Al₂O₃, 10-30% CaO, 5-15% MgO, 3˜10% SiO₂, and a small amount of impurities.
 6. The agent for steel-making according to claim 5, wherein said deoxidizing agent or modifying agent for steel-making consists of the following compositions by mass percentage: 25-70% Al, 3-30% Al₂O₃, 10-30% CaO, 5-15% MgO, 3˜10% SiO₂, <3% rare earth elements, and a small amount of impurities.
 7. The agent for steel-making according to claim 6, wherein each composition in said deoxidizing agent or modifying agent for steel-making is powdered shaped, with a granularity of 50 μm˜1 mm.
 8. The agent for steel-making according to claim 7, wherein said deoxidizing agent or modifying agent powder for steel-making is pressed into a sphere shape.
 9. The agent for steel-making according to claim 8, wherein said deoxidizing agent or modifying agent powder for steel-making, which has been pressed into a sphere shape, has a diameter of 20˜50 mm
 10. The agent for steel-making according to claim 7 or 8, wherein said deoxidizing agent or modifying agent for steel-making is added to the molten steel during molten steel tapping in primary melting of a converter or electric furnace.
 11. The agent for steel-making according to claim 7 or 8, wherein said deoxidizing agent or modifying agent for steel-making is added to a ladle refining furnace or electric furnace.
 12. The agent for steel-making according to claim 4, wherein said slag regulating agent for steel-making comprises by mass percentage 5-20% Al, 25-70% Al₂O₃, 10-50% CaO, 5-15% MgO, 3˜10% SiO₂, and a small amount of impurities.
 13. The agent for steel-making according to claim 12, wherein said slag regulating agent for steel-making consists of the following compositions by mass percentage: 5-20% Al, 25-70% Al₂O₃, 10-50% CaO, 5-15% MgO, <3% rare earth elements, 3˜10% SiO₂, and a small amount of impurities.
 14. The agent for steel-making according to claim 13, wherein each composition in said slag regulating agent for steel-making is powdered shaped or is sphere shaped by pressing powders.
 15. The agent for steel-making according to claim 14, wherein said slag regulating agent for steel-making is added to a ladle refining furnace for slag regulating, or is added to molten steel for slag regulating during molten steel tapping in primary melting of a converter or electric furnace.
 16. The agent for steel-making according to claim 11, wherein said deoxidizing agent or modifying agent powder for steel-making is blown into a ladle refining furnace or electric furnace.
 17. The agent for steel-making according to claim 12, wherein during steel tapping in a converter, said deoxidizing agent or modifying agent for steel-making is added once the addition of Fe alloys is complete.
 18. The agent for steel-making according to claim 17, wherein during steel tapping in the converter, when ⅓ of the steel has been tapped, ⅔ of the deoxidizing agent or modifying agent for steel-making is added, and then when the steel tapping is complete, the remaining ⅓ deoxidizing agent or modifying agent for steel-making is added to the surface of the ladle refining furnace.
 19. The agent for steel-making according to claim 15, wherein the dosage of said slag regulating agent for steel-making is selected so that MgO in the furnace slag reaches a saturation value. 